1. Technical Field of the Invention
The present invention generally relates to Ethernet OAM networks. More particularly, and not by way of any limitation, the present invention is directed to a system and method for propagating fault information and suppressing alarm indication signaling in an Ethernet OAM network.
2. Description of Related Art
The link between the end user and the public network, essential key to the delivery of broadband applications to residential and business subscribers, is known by many names, e.g., first mile, last mile, local loop, metro access, subscriber access network, etc., and is implemented using a variety of different transport technologies and protocols over diverse physical connections. For instance, today most users connect to the public network with Digital Subscriber Line (DSL), Integrated Services Digital Network (ISDN), cable TV, T1/E1 or T3/E3 lines, using Synchronous Optical Network and its companion Synchronous Digital Hierarchy (SONET/SDH), Frame Relay and Asynchronous Transfer Mode (ATM). Regardless of the nomenclature or the actual implementation, all access networks require operations, administration and maintenance (OAM) support features to ensure the maintainability and uptime required to provide broadband services.
Current first/last mile solutions have significant shortcomings from the customer's perspective, ranging from performance bottlenecks, fixed bandwidth provisioning, limited scalability, lack of flexibility and provisioning complexity to end-to-end quality of service (QoS) issues and a high cost structure. The use of robust, simple Ethernet technology in the first mile promises to revolutionize the access network as it did the enterprise network. Ethernet is a local area network (LAN) transport technology that is used ubiquitously in the home and in business to communicate between computers and networks. As an access technology, Ethernet offers three significant advantages over legacy first mile technologies: (i) future-proof transport for data, video and voice applications; (ii) cost-effective infrastructure for data services; and (iii) simple, globally accepted standard that will ensure interoperability.
In order to adapt the Ethernet technology in a carrier-grade service environment, various standards are being developed that aim to provide advanced OAM capabilities (also referred to as Ethernet Connectivity and Fault Management or Ethernet CFM) across the entire network from one end to the other end. Since the end-to-end service network environment is typically comprised of a patchwork of diverse component networks (e.g., metro access networks and core networks using a variety of technologies) that may belong to different organizations, network operators and service providers, the Ethernet OAM plane is envisioned as a hierarchically layered domain space wherein specific OAM domains are defined corresponding to the constituent network infrastructure and provisioning. In particular, two standards, IEEE 802.1ag and ITU-T (Question 3, Study Group 13), incorporated by reference herein, that are specifically concerned with end-to-end Ethernet OAM define a customer-level domain at the highest level of hierarchy, which comprises one or more provider domains (occupying an intermediate level), each of which in turn includes one or more operator domains disposed at a lower hierarchical level. By way of standardization, the OAM domain space may be partitioned into up to a number of levels, e.g., 8 levels, each domain corresponding to a particular level, wherein a domain is defined in terms of what are referred to as flow points. In the context of the IEEE 802 specification suite, the flow points are new entities contained in Media Access Control (MAC) “interfaces” and “ports” as defined in related standards documentation. A flow point at the edge of an OAM domain is called a “Maintenance End Point” or MEP. A flow point inside a domain and visible to a MEP is called a “Maintenance Intermediate Point” or MIP. Whereas MEP nodes are used by system administrators to initiate and monitor OAM activity (by issuing appropriate OAM frames), MIP nodes passively receive and respond to OAM flows initiated by MEP nodes. An OAM domain having one or more MIP nodes is bounded by two or more MEP nodes, wherein a “Maintenance Entity” (ME) is defined to include a set of MIP nodes disposed between one MEP node and another MEP node. Thus it is possible to have more than one ME in a particular OAM domain.
Although the Ethernet OAM architecture as currently being standardized provides an impressive framework for addressing end-to-end Ethernet Connectivity and Fault Management at any level of the OAM hierarchy, a number of issues remain to be solved as will be set forth in detail hereinbelow.